How to Prune Lilac Bushes

Lilac bushes are a popular fixture in many gardens because of their gorgeous purple color and their heady fragrance. Pruning your lilac bush is the best way to ensure that it continues blooming year after year while remaining a manageable height. Lilac bushes can grow to 30 feet (9 meters) high without consistent care. Read the tips listed below and learn to prune your lilac bushes.

Prune with sharp gardening shears.

Prune your lilac bush when it is 6 to 8 feet (183 to 244 centimeters) tall.

Prune the stems after the bush has finished blooming. This is usually in the spring. If you wait until the summer or fall to prune, you may be cutting off next year's flowers. Lilacs, unlike other bushes, grow on old wood. The later you prune, the more old wood you prune and the less blooms will grow next year [source: Country Living].

Prune significantly. Though other bushes may only require that the tops of the stems be cut, it's better to cut the entire stem off the lilac. Remove dead flowers all the way until the stem to prevent seeding. When you're done pruning, you should have cut away about a third of the branches [source: Phipps].

Prune the bush until it's 6 to 8 inches (15 to 20 centimeters) tall, if your lilac bush has become unattractive and you want to start fresh. This will ensure healthy flowers when the bush begins to bloom again. Keep in mind that it may take up to three years to see flowers [source: Phipps].